The present invention relates to a timer apparatus which is arranged so that a power source, a timer unit for outputting time information and a control unit for controlling the timer unit are molded, and a time can be changed, and relates to a computer having such the timer apparatus.
In a system utilizing a computer such as a remittance system and electronic filing document transmission system, since an outputted time occasionally has important meaning, it is desired that the computer is provided with a timer apparatus in which a time is not changed incorrectly.
As a technique for preventing an incorrect change of a time in a timer apparatus, U.S. Pat. No. 5,001,752 discloses a digital time authentication apparatus in which a whole apparatus is fixed integrally by an epoxy resin and a switch is provided so as to be embedded into the epoxy resin and when the switch is turned on, the apparatus is exploded by a physical destruction activity, or a digital time authentication apparatus which performs signature communication and encryption communication in order to make it difficult to change software from an input terminal.
However, in the digital time authentication apparatus in which the switch is provided so as to be embedded into the epoxy resin, an input terminal can be dug out by X-raying so that the switch is not turned on, and in the digital time authentication apparatus which performs signature communication and encryption communication, a skilled cracker can find signature and cipher key.